A more appropriate name for a bat nursery is a maternity roost.
Most bat species give live birth to only one pup per year. However, some species can give birth to twins or multiple pups. For 3 to 4 weeks, the baby is incapable of flying and is latched onto its mother’s nipple. It is not until they are about five weeks old that the baby bat can begin flying lessons and leaves its roost.
Well considering there are several billion bats in the world that is an exceptional amount of rabies